[Solved] CSVReader headerReader = new CSVReader(new FileReader(this.getClass().getResource(filePath).getPath()), delimiter);

by



CSVReader headerReader = new CSVReader(new FileReader(this.getClass().getResource(filePath).getPath()), delimiter);

solved CSVReader headerReader = new CSVReader(new FileReader(this.getClass().getResource(filePath).getPath()), delimiter);